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15 Stormwater Report Updated 8-21-20
2131 GRAF MASTER SITE PLAN LOT 2, MINOR SUB. 235 STORMWATER DESIGN REPORT A. Introduction This design report will give an overview of the proposed stormwater system for the 26-acre Graf Street Apartments Master Site Plan located in Lot 2 of Minor Sub. 235, Section 23, T02 S., R05 E., Bozeman, Montana. The project site is broken into two phases of development. Phase 1 includes the extension of Lantern Drive, South 21st Avenue, required parkland, and development of the northern half of the net lot areas. Phase 2 will consist of the development of the southern half of the net lot areas. The proposed storm water management system consists of overland sheet flow, curb and gutter, sidewalk chases, and swales to direct runoff towards either permeable paver infiltration systems and gravel infiltration systems for on-site development, or underground retention chambers for S 21st Ave. Lantern Drive was not included in this report, because it was previously accounted for in the Nexus Point stormwater design report. Nexus Point is the adjacent project to the north, which will be constructed prior to this project. The following references were used in the preparation of this report: a. COB Design Standards and Specifications Policy, 2004. Addendum #7 b. COB Modifications to Montana Public Works Standard Specifications (MPWSS) The delineated basins, drainage plans, grading plans, and details are displayed on the sheets in Appendix A. B. Runoff and Basin Estimates 25-year storm event runoff rates were calculated for the pertinent basins utilizing the rational method in accordance with the COB design standards. A runoff coefficient C of 0.71 was determined for the total developable area of the site. The total developable area includes the net lot areas, roadway and trail easements, but excludes the areas of Lantern Park and the watercourse setbacks. Area C Total Area 897,198 NA Impervious 657626 0.9 Landscaped 239572 0.2 Weighted C NA 0.71 Basins 9 and 10 are the basins of concern for conveyance sizing as they are the basins for S 21st Ave. Runoff from these basins is conveyed via curb and gutter to two curb inlets, and is then piped to underground retention chambers. The 25-year flow rates for basins 9 & 10 are 2.0 cfs and 1.9 cfs respectively, calculations are included in Appendix B. C. Conveyance Capacity The proposed infrastructure improvements were designed to convey runoff per the City of Bozeman standards. The conveyance structures include concrete curb-gutter and storm drain piping. The curb & gutter capacity at the minimum project slope of 1% without overtopping a depth of 0.15’ below the top of the curb is 4.04 cfs, exceeding the peak runoffs. Runoff from Basins 9 & 10 enters storm drain curb inlets and is then piped to underground retention chambers. The storm drain piping was sized to be 15” diameter PVC. Calculations are included in Appendix B. Lantern Drive was not included in this report, because it was previously accounted for in the Nexus Point stormwater design report. The previous report indicated that 15” diameter PVC would be sufficient for the Lantern Drive inlets. D. Inlet Grate Sizing The curb inlet that receives runoff from drainage basins 9 and 10 were checked for capacity. The selected inlet has a capacity of 2.51 cfs. This exceeds the maximum 25-year storm runoff tributary to that point of 2.0 cfs. Calculations are included in Appendix B. The selected nyloplast 8” area drains have a capacity of 0.32 cfs at the design head of 0.25’. Basin 7 has an estimated 25-year peak runoff of 2.5 cfs, which would require 8 inlet drains. Adequate area inlets have been provided to meet the incoming peak runoff. The manufacturer’s flow rate information is included in Appendix B. E. Native Gravel Infiltration Rates The infiltration rate of native gravels was determined using a constant-head test. Two test pits were utilized for testing (TP-01 and TP-51). See Appendix C for a test pit location map. Each test pit was pre-soaked with approximately 60 gallons of water before testing. The pre-soak period was completed to simulate a saturated ground condition prior to performing the constant- head test. Two tests were completed at each test pit. The average infiltration rate was found to be 2.76 inches per minute. Providing a factor of safety of 2, the design of the pervious pavers used an infiltration rate of 1.38 inches per minute. The infiltration rate of the native gravels is much less than that of the block pavers, so the native gravels control. See Appendix C for infiltration rate calculations. F. Stormwater Detention/Retention Volumes and Infiltration System Calculations All of the Runoff is proposed to be conveyed to underground storage systems and ultimately infiltrate into native gravels. Three types of underground systems are proposed: pervious pavers, area drain inlets with perforated pipe wrapped in drain rock, and Contech retention chambers. Groundwater monitoring was conducted to determine the seasonal high groundwater levels. Groundwater monitoring data is included in Appendix D. The groundwater depth below existing grade is summarized in the table below: Groundwater Depth Below Existing Grade (ft) Date Well 1 Well 2 Well 3 Well 4 5/8/2020 5.37 0.00 0.00 6.49 5/15/2020 5.57 5.65 4.65 6.58 5/27/2020 5.94 5.75 4.67 6.68 6/5/2020 5.73 6.00 4.85 6.64 6/12/2020 4.54 5.98 4.80 6.45 6/19/2020 4.17 5.93 4.62 6.22 6/26/2020 4.64 5.89 4.64 6.41 7/3/2020 4.55 6.00 4.58 6.30 7/13/2020 5.81 6.11 4.89 6.62 7/20/2020 4.76 5.32 4.64 6.56 7/27/2020 4.52 5.56 4.77 6.52 Min 4.17 5.32 4.58 6.22 Max 5.94 6.11 4.89 6.68 The seasonal groundwater data was then utilized to model the seasonal high groundwater surface. The surface was used to approximate the seasonal high groundwater level at the location of all the buried storage and infiltration facilities. The bottom of the storage elevation was then set to be above the seasonal high groundwater. The storage areas and volumes were sized based on the depth to groundwater. Figures 1 and 2 of the geotechnical report, which are included in Appendix D, were used to approximate the depth of native gravel. The proposed storage systems, bottom of retention storage elevations, seasonal high groundwater elevations, approximate depths to gravel, and approximate native gravel elevations are summarized in the following table, additional information is included in Appendix E: Groundwater Surface & Gravel Depth Summary Location Bottom of Retention Storage Elevation (ft) Seasonal High Groundwater Surface Elevation (ft) Nearest Test Pit *Figure 1 of Geotech Approximate Depth to Gravel (ft) *Figure 2 of Geotech Estimated Native Gravel Elevation (ft) Basin 1 Pervious Pavers 4961.68 4961.25 TP-17 3.8 4962.2 Basin 2 Pervious Pavers 4964.26 4961 TP-18 5.1 4963.4 Basin 3 Pervious Pavers 4964.77 4964.5 TP-52 1.9 4968.1 Basin 4 Pervious Pavers 4967.74 4967.5 TP-49 1.5 4970.5 Basin 5 Pervious Pavers 4970.24 4967.75 TP-11 3.0 4972 Basin 6 Pervious Pavers 4969.34 4969 TP-43 3.7 4970.3 Basin 7 Infiltration System 4961 4961 TP-01 2.9 4961.1 Basin 8 Pervious Pavers 4972.5 4968 TP-27 3.2 4973.8 Basin 9 & 10 Retention Chambers 4963 4962.5 TP-34 4.0 4965 Basin 11 Infiltration System 4963 4960 TP-17 3.8 4960.2 The detention and retention storage volumes were sized based on the depth to high groundwater and on a 10 year 2 hour event per the City Design Standards. Detention systems were sized to include infiltration rates. The Retention system serving the public street, S 21st Ave, was sized to totally retain the 10 year 2 hour storm per the City Engineering Department’s request. The City did not want to include infiltration in the equations for the public street Retention System. The calculations for all stormwater storage facilities are included in Appendix E. The proposed stormwater facilities reduce the Post-development runoff rate to zero. All runoff is conveyed to the infiltration retention and detention systems and then infiltrates into the ground. In the event that a storm greater than the design storm occurs, emergency overflows route runoff onto street drainage systems, minimizing damage to buildings or structures. G. Stormwater Facility Maintenance The proposed storm drainage facilities will be privately operated and maintained by the property owners association of the on-site development. The POA covenants should include provisions for storm water maintenance included in Appendix E. Appendices A. Drawings and Details B. Runoff, Conveyance, and Inlet Calculations C. Test Pit Location Map and Infiltration Calculations D. Groundwater Monitoring Data and Geotech Report Figures E. Detention and Retention Calculations F. Stormwater Maintenance Plan Appendices Appendix A – Drawings and Details PUBLIC PARK BLDG 4 TYPE B 2171 GRAF ST BLDG 2 TYPE C 2161 GRAF ST BLDG 6 TYPE B 2179 GRAF ST BLDG 5 TYPE A 2175 GRAF ST BLDG 19 TYPE B 2141 GRAF ST BLDG 16 TYPE C 2155 GRAF ST BLDG 17 CLUB HOUSE 2131 GRAF ST BLDG 3 TYPE D 2171 GRAF BLDG 10 TYPE B 2065 GRAF ST BLDG 13 TYPE C 2051 GRAF ST BLD G 1 5 T Y P E A 2061 G R A F S T BLDG 21 TYPE B 2151 GRAF ST BLDG 18 TYPE C 2135 GRAF ST BLDG 20 TYPE B 2145 GRAF ST BLDG 12 TYPE C 2069 GRAF ST BLDG 7 TYPE B 2181 GRAF ST BLDG 1 TYPE E CLUB HOUSE 2079 GRAF ST BLDG 8 TYPE B 2071 GRAF ST BLDG 9 TYPE B 2075 GRAF ST BLDG 11 TYPE A 2067 GRAF ST BASIN 11 22915 SF BASIN 5 183041 SF BASIN 10 63983 SF BASIN 9 66769 SF BASIN 3 51818 SF BASIN 6 126106 SF LANTERN DRIVE S 2 1 S T A V E S 2 1 S T A V E WEST GRAF ST S 1 9 T H A V E BASIN 1 160623 SF BASIN 7 82565 SF BASIN 2 15581 SF BASIN 4 48789 SF BASIN 8 17555 SF 1" = 0 SCALE 70 1403570 SHEET MA D I S O N E N G I N E E R I N G 89 5 T E C H N O L O G Y B L V D , S U I T E 2 0 3 BO Z E M A N , M T 5 9 7 1 8 (4 0 6 ) 5 8 6 - 0 2 6 2 ( 4 0 6 ) 5 8 6 - 5 7 4 0 F A X 2131 GRAF STORM DRAIN SD1.1 21 3 1 G R A F ST O R M D R A I N A G E B A S I N E X H I B I T LEGEND BO Z E M A N , M T PUBLIC PARK BLDG 4 TYPE B 2171 GRAF ST BLDG 2 TYPE C 2161 GRAF ST BLDG 6 TYPE B 2179 GRAF ST BLDG 5 TYPE A 2175 GRAF ST BLDG 19 TYPE B 2141 GRAF ST BLDG 16 TYPE C 2155 GRAF ST BLDG 17 CLUB HOUSE 2131 GRAF ST BLDG 3 TYPE D 2171 GRAF BLDG 10 TYPE B 2065 GRAF ST BLDG 13 TYPE C 2051 GRAF ST BLD G 1 5 T Y P E A 206 1 G R A F S T BLDG 21 TYPE B 2151 GRAF ST BLDG 18 TYPE C 2135 GRAF ST BLDG 20 TYPE B 2145 GRAF ST BLDG 12 TYPE C 2069 GRAF ST BLDG 7 TYPE B 2181 GRAF ST BLDG 1 TYPE E CLUB HOUSE 2079 GRAF ST BLDG 8 TYPE B 2071 GRAF ST BLDG 9 TYPE B 2075 GRAF ST BLDG 11 TYPE A 2067 GRAF ST F.F. ELEV 4973.0 F.F. ELEV 4968.0 F.F. ELEV 4974.9 F.F. ELEV 4969.6 F.F. ELEV 4968.1 F.F. ELEV 4970.9 F.F. ELEV 4977.4± F.F. ELEV 4972.6 F.F. ELEV 4975.0 F.F. ELEV 4977.3 F.F. ELEV 4983.0 F.F. ELEV 4977.50± F.F. ELEV 4973.00 F.F. ELEV 4978.8±F.F. ELEV 4977.0± F.F. ELEV 4982.0± F.F. ELEV 4979.5± F.F. ELEV 4982.5± F.F. ELEV 4978.2± F.F. E L E V 4978 . 5 ± SHEET MA D I S O N E N G I N E E R I N G 89 5 T E C H N O L O G Y B L V D S U I T E 2 0 3 BO Z E M A N , M T 5 9 7 1 8 (4 0 6 ) 5 8 6 - 0 2 6 2 1 inch = 0 SCALE 50' 100'25'50' 2131 GRAF GRADING PLAN C0.5 GRAF STREET S 1 9 T H AV E N U E PROPOSED PUBLIC PARK LANTERN DR OV E R A L L G R A D I N G P L A N 21 3 1 G R A F BO Z E M A N , M T LEGEND PHASE I EAST PHASE I WEST FUTURE PHASE WEST FUTURE PHASE EAST SO U T H 2 1 S T A V E N U E PUBLIC PARK BLDG 4 TYPE B 2171 GRAF ST BLDG 2 TYPE C 2161 GRAF ST BLDG 6 TYPE B 2179 GRAF ST BLDG 5 TYPE A 2175 GRAF ST BLDG 3 TYPE D 2171 GRAF BLDG 7 TYPE B 2181 GRAF ST BLDG 1 TYPE E CLUB HOUSE 2079 GRAF ST BLDG 8 TYPE B 2071 GRAF ST BLDG 9 TYPE B 2075 GRAF ST LANTERN DRIVE (CONSTRUCTED WITH NEXUS POINT) S 2 1 S T A V E S 2 1 S T A V E 1" = 0 SCALE 40 802040 SHEET MA D I S O N E N G I N E E R I N G 89 5 T E C H N O L O G Y B L V D , S U I T E 2 0 3 BO Z E M A N , M T 5 9 7 1 8 (4 0 6 ) 5 8 6 - 0 2 6 2 ( 4 0 6 ) 5 8 6 - 5 7 4 0 F A X 2131 GRAF DRAINAGE PLAN C1.5 21 3 1 G R A F PH A S E 1 D R A I N A G E P L A N LEGEND BO Z E M A N , M T BLDG 6 TYPE B 2179 GRAF ST BLDG 19 TYPE B 2141 GRAF ST BLDG 16 TYPE C 2155 GRAF ST BLDG 17 CLUB HOUSE 2131 GRAF ST BLDG 10 TYPE B 2065 GRAF ST BLDG 13 TYPE C 2051 GRAF ST BLD G 1 5 T Y P E A 206 1 G R A F S T BLDG 21 TYPE B 2151 GRAF ST BLDG 18 TYPE C 2135 GRAF ST BLDG 20 TYPE B 2145 GRAF ST BLDG 12 TYPE C 2069 GRAF ST BLDG 7 TYPE B 2181 GRAF ST BLDG 8 TYPE B 2071 GRAF ST GRAF ST BLDG 11 TYPE A 2067 GRAF ST FUTURE PHASE FUTURE PHASE S 2 1 S T A V E WEST GRAF ST 1" = 0 SCALE 40 802040 SHEET MA D I S O N E N G I N E E R I N G 89 5 T E C H N O L O G Y B L V D , S U I T E 2 0 3 BO Z E M A N , M T 5 9 7 1 8 (4 0 6 ) 5 8 6 - 0 2 6 2 ( 4 0 6 ) 5 8 6 - 5 7 4 0 F A X 2131 GRAF DRAINAGE PLAN C1.6 21 3 1 G R A F FU T U R E P H A S E D R A I N A G E P L A N LEGEND BO Z E M A N , M T BLDG 4 TYPE B 2171 GRAF ST BLDG 2 TYPE C 2161 GRAF ST BLDG 6 TYPE B 2179 GRAF ST BLDG 5 TYPE A 2175 GRAF ST BLDG 3 TYPE D 2171 GRAF BLDG 7 TYPE B 2181 GRAF ST BLDG 1 TYPE E CLUB HOUSE 2079 GRAF ST 1 inch = 0 SCALE 30' 60'15'30' SHEET MA D I S O N E N G I N E E R I N G 89 5 T E C H N O L O G Y B L V D S U I T E 2 0 3 BO Z E M A N , M T 5 9 7 1 8 (4 0 6 ) 5 8 6 - 0 2 6 2 2131 GRAF GRADING PLAN C1.7 GR A D I N G P L A N - P H A S E I E A S T 21 3 1 G R A F BO Z E M A N , M T LANTERN DRIVE CONSTRUCTED WITH NEXUS POINT FUTURE PHASE PHASE I EAST SEE SHT C1.8 SO U T H 2 1 S T AV E N U E PHASE LINE FUTURE PHASE LEGEND PUBLIC PARK BLDG 2 TYPE C 2161 GRAF BLDG 1 TYPE E CLUB HOUSE 2079 GRAF ST BLDG 8 TYPE B 2071 GRAF ST BLDG 9 TYPE B 2075 GRAF ST SHEET MA D I S O N E N G I N E E R I N G 89 5 T E C H N O L O G Y B L V D S U I T E 2 0 3 BO Z E M A N , M T 5 9 7 1 8 (4 0 6 ) 5 8 6 - 0 2 6 2 1 inch = 0 SCALE 30' 60'15'30' 2131 GRAF GRADING PLAN C1.8 GR A D I N G P L A N - P H A S E I W E S T 21 3 1 G R A F BO Z E M A N , M T SO U T H 1 9 T H A V E N U E LANTERN DRIVE SO U T H 2 1 S T AV E N U E LEGEND FUTURE PHASE PHASE I WEST SEE SHT C1.7 PHASE LINE DETAIL1 C2.2 CMP ROUND PERFORATED PIPE - RETENTION/INFILTRATION SYSTEM DETAIL3 C2.2 CONCRETE VALLEY GUTTER DETAIL4 C2.2 CURB CHASE DETAIL2 C2.2 PERVIOUS PAVER DETAIL DETAIL5 C2.2 GRAVEL INFILTRATION SYSTEM DETAIL6 C2.2 PARK PLAYGROUND INFILTRATOR SHEET MA D I S O N E N G I N E E R I N G 89 5 T E C H N O L O G Y B L V D S U I T E 2 0 3 BO Z E M A N , M T 5 9 7 1 8 (4 0 6 ) 5 8 6 - 0 2 6 2 ( 4 0 6 ) 5 8 6 - 5 7 4 0 F A X 2131 GRAF CIVIL DETAILS C2.2 21 3 1 G R A F CI V I L D E T A I L S BO Z E M A N , M T 11.75" 13.7"END VIEWTOP VIEW T O P V I E W I N T E R C O N N E C T E D B L O C K S 4.5"1"10"R 0 . 2 5 " 4" 1 0 . 2 5 " D R A I N A G E S P A C E R 0.5"R0.5" 0 . 2 5 " 4 5 ° 1 " X 1 4 " A A S I D E V I E W 0 . 2 5 " O P E N J O I N T ( T Y P ) P O W E R B L O C K ( S I D E V I E W ) 6 " M I N . * * 3 4 " - 1 " C L E A N , W A S H E D A N G U L A R S T O N E S E C T I O N A - A V I E W A C F M 2 0 0 W O V E N G E O T E X T I L E ( O R A S S H O W N O N P L A N S ) 1 4 " O P E N J O I N T * S U B G R A D E T O B E P R E P A R E D P E R E N G I N E E R O F R E C O R D ' S S P E C I F I C A T I O N S ( S E E P L A N S ) A C F P O W E R B L O C K O P E N J O I N T P A V E R F O R A D D I T I O N A L I N F O R M A T I O N P L E A S E C O N T A C T : A C F E N V I R O N M E N T A L , 1 - 8 0 0 - 4 4 8 - 3 6 3 6 , w w w . a c f e n v i r o n m e n t a l . c o m 0 7 / 0 7 / 1 7 * 14" OPEN JOINTS SHALL BE UNFIL L E D AND FREE OF STONE/SAND BACK F I L L . ** RECOMMENDED STONE BAS E D E P T H S DEPTHS LISTED BELOW ARE SU B J E C T T O CBR TESTS AND THE DESIGN E N G I N E E R ' S SUBGRADE SUPPORT CALCUL A T I O N S . PEDESTRIAN TRAFFIC 6 " - 8 " M I N . PASSENGER VEHICLE TRAFFIC 1 2 " M I N . INDUSTRIAL TRAFFIC 1 8 " M I N . Appendix B – Runoff, Conveyance, and Inlet Calculations Drainage Basin No.Area (Ac.) Weighted C 100 Yr 25 Yr 10 Yr 7 1.895 0.71 4.4 2.5 1.8 9 1.533 0.71 3.5 2.0 1.4 10 1.469 0.71 3.4 1.9 1.4 General Equation:i = a/(b+D)n where D is duration in hours, i = intensity in inches/hour Design Rainfall Freq.100 25 10 IDF coefficient a 1.01 0.78 0.64 IDF coefficient b 0 0 0 IDF coefficient n 0.67 0.64 0.65 Adjustment Factor Cf:1.25 1.1 1 Area C Total Area 897,198 NA Impervious 657,626 0.9 Landscaped 239,572 0.20 Weighted C NA 0.71 Drainage Basin 7 Area 1.90 acres 0.71 1.00 percent 700 feet Design Rainfall Freq. 100 25 10 years C*Cf 0.89 0.78 0.71 (Shall not exceed 1.00) Total tc:10.51 15.78 19.30 minutes intensity at tc 3.24 1.83 1.34 in/hr 4.37 2.47 1.80 cfs Drainage Basin 9 Area 1.53 acres 0.71 1.30 percent 900 feet Design Rainfall Freq. 100 25 10 years C*Cf 0.89 0.78 0.71 (Shall not exceed 1.00) Total tc:10.72 16.22 19.89 minutes intensity at tc 3.20 1.80 1.31 in/hr 3.50 1.97 1.43 cfs Drainage Basin 10 Area 1.47 acres 0.71 1.30 percent 900 feet Design Rainfall Freq. 100 25 10 years C*Cf 0.89 0.78 0.71 (Shall not exceed 1.00) Total tc:10.72 16.22 19.89 minutes intensity at tc 3.20 1.80 1.31 in/hr 3.35 1.89 1.37 cfs Runoff Coefficient Peak Q values Graf Street Apartments, Lot 2 of Minor Sub. 235 Peak Flow Summary (cfs) Storm Information IDF Equations from Bozeman Stormwater Master Plan for City of Bozeman, March 1982 Peak flow calculations Curb Inlet Drainage Areas - Post Development See SD1.1 for visual reference Weighted C Average slope peak runoff: Travel Distance Weighted C Average slope Travel Distance Weighted C Average slope Travel Distance peak runoff: peak runoff: Allowable Pavement Encroachment Given: T =9 feet (max per city) W =1.5 feet Ts =7.5 feet Sw =0.0625 ft/ft Sx =0.03 ft/ft a =0.59 inches d =3.24 inches n =0.015 Sw/Sx =2.08 T/W =6 Capacity for Gutter equations: Where: Qs = Discharge within the Roadway above the depressed section (cfs) Qw = Discharge within the depressed (gutter) section (cfs) Cf = 0.56 for English units Sx = Pavement cross slope (ft/ft) Ts = Width of flow in the roadway above depressed section So = Gutter longitudinal slope (ft/ft) Sw = Gutter depression cross slope (ft/ft) T = Spread (ft) W = Width of gutter depression (ft) Capacity solution Gutter Capacity - Drainage Basin 9 Gutter Capacity - Drainage Basin 10 So =0.0100 So =0.0100 Qs =2.33 cfs Qs =2.33 cfs Eo =0.42 cfs Eo =0.42 cfs Q =4.04 cfs Q =4.04 cfs A=1.215 sf A=1.215 sf V=3.33 ft/s V=3.33 ft/s BASIN Gutter Capacity (cfs) 25 Yr Design Flow (cfs) Capacity greater than 25- yr flow? 9 4.04 1.97 Yes 10 4.04 1.89 Yes Summary Gutter Capacity Calculations The gutter capacity is adequate for each drainage area. Graf Street Apartments, Lot 2 of Minor Sub. 235 SWQQQ QEQoW 0 S E1 QQ 2 1 O3 8 S3 5 X f S STSn CQ 1 8/3 XW XWo 11T/W /SS1 /SS1E Gutter Section Given:T =9.0 feet W =1.50 feet Ts =7.50 feet Sw =0.0625 ft/ft Sx =0.03 ft/ft a =0.59 inches d =3.24 inches n =0.015 Where: Qs =Discharge within the Roadway above the depressed section (cfs) Qw =Discharge within the depressed (gutter) section (cfs) Capacity for Inlets on Grade Cf =0.56 for English units (Standard 24x36 Curb inlet)Sx =Pavement cross slope (ft/ft) Ts =Width of flow in the roadway above Drainage Basin 9 depressed section So =Gutter longitudinal slope (ft/ft) Qw =1.95 cfs Sw =Gutter depression cross slope (ft/ft) Qs =2.66 cfs T =Spread (ft) Cross-sectional area of flow W =Width of gutter depression (ft) A =1.22 ft2 Gutter Velocity V =3.79 ft/sec Fraction of side flow intercepted Rs =0.18 Total flow capacity intercepted by the inlet Qint =2.51 cfs Qbypass =2.10 cfs Design Q for inlet #1 Q25 =1.97 cfs Single Inlet Sufficient Drainage Basin 10 Qw =1.95 cfs Qs =2.66 cfs Cross-sectional area of flow A =1.22 ft2 Gutter Velocity V =3.79 ft/sec Fraction of side flow intercepted Rs =0.18 Total flow capacity intercepted by the inlet Qint =2.51 cfs Qbypass =2.10 cfs Design Q for inlet #2 Q25 =1.89 cfs Single Inlet Sufficient Inlet Capacity Calculations Graf Street Apartments, Lot 2 of Minor Sub. 235 3130 Verona Avenue • Buford, GA 30518 (866) 888-8479 / (770) 932-2443 • Fax: (770) 932-2490 © Nyloplast Inlet Capacity Charts June 2012 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 0.60 0.65 0.70 0.75 0.80 0.85 0.90 0.95 1.00 1.05 1.10 Ca p a c i t y ( c f s ) Head (ft) Nyloplast 8" Drop In Grate Inlet Capacity Chart Basin 9 & 10 Pipe Sizing CIRCULAR CHANNEL Manning's Eqn.1.486 A R2/3 S1/2 n Diameter,do (in) =15.0 Diameter,do (ft) =1.25 Units =1.486 n =0.015 Slope, S (ft/ft)0.005 Depth, y (ft) Theta (rad) Area, A (ft2) Wetted Perimeter, P (ft) Hydraulic Radius, R (ft) Top Width, T (ft) Hydraulic Depth, D (ft) Section Factor, Z (ft5/2) Q (cfs) Q (gpm) Q (gpd - 8 hour day) V (ft/s) Energy, E = V2/2g (ft) 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.0 0.0 0.0 0.00 0.06 0.90 0.02 0.56 0.04 0.54 0.04 0.00 0.02 8.5 4095.3 0.8 0.01 0.13 1.29 0.06 0.80 0.08 0.75 0.09 0.02 0.08 37.1 17804.7 1.3 0.03 0.19 1.59 0.12 0.99 0.12 0.89 0.13 0.04 0.19 86.4 41454.3 1.7 0.04 0.25 1.85 0.17 1.16 0.15 1.00 0.17 0.07 0.35 155.6 74681.3 2.0 0.06 0.31 2.09 0.24 1.31 0.18 1.08 0.22 0.11 0.54 243.4 116818.8 2.3 0.08 0.38 2.32 0.31 1.45 0.21 1.15 0.27 0.16 0.78 347.9 167005.9 2.5 0.10 0.44 2.53 0.38 1.58 0.24 1.19 0.32 0.22 1.04 467.2 224236.5 2.7 0.11 0.50 2.74 0.46 1.71 0.27 1.22 0.37 0.28 1.33 598.7 287385.0 2.9 0.13 0.56 2.94 0.54 1.84 0.29 1.24 0.43 0.35 1.65 740.0 355218.7 3.1 0.15 0.63 3.14 0.61 1.96 0.31 1.25 0.49 0.43 1.98 888.3 426402.7 3.2 0.16 0.69 3.34 0.69 2.09 0.33 1.24 0.56 0.52 2.32 1040.6 499497.4 3.4 0.17 0.75 3.54 0.77 2.22 0.35 1.22 0.63 0.61 2.66 1193.6 572948.9 3.5 0.19 0.81 3.75 0.84 2.34 0.36 1.19 0.71 0.71 2.99 1343.9 645069.1 3.5 0.20 0.88 3.96 0.92 2.48 0.37 1.15 0.80 0.82 3.31 1487.5 714000.7 3.6 0.20 0.94 4.19 0.99 2.62 0.38 1.08 0.91 0.94 3.61 1620.1 777654.1 3.7 0.21 1.00 4.43 1.05 2.77 0.38 1.00 1.05 1.08 3.87 1736.6 833588.9 3.7 0.21 1.06 4.69 1.11 2.93 0.38 0.89 1.25 1.24 4.08 1830.8 878765.1 3.7 0.21 1.13 5.00 1.16 3.12 0.37 0.75 1.55 1.45 4.22 1893.6 908917.6 3.6 0.20 1.19 5.38 1.20 3.36 0.36 0.54 2.21 1.79 4.25 1909.1 916351.7 3.5 0.19 1.25 6.28 1.23 3.93 0.31 0.00 3.96 1777.3 853093.6 3.2 0.16 Basin 9 + 10 Q =3.86 cfs Capacity?OK Q = 0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 4.50 0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40 Depth (ft) Q (CFS) V (ft/s) E (ft) y do T THETA Appendix C – Test Pit Location Map and Infiltration Calculations Project Name:Graf St. Apartments Test Number:1 (TP-01 on map) Diameter of Test Hole:24"Depth of Test Hole:9.83 ft. Date and Time Soak Period Began: 4/3/20 @ 9:00 am Ended: 4/3/20 @ 10:15 am Date Test Began:4/3/2020 9.83 ft. Test Results Start Time of Day End Time of Day Time Interval (Minutes) Initial Distance Below Reference Point (ft.) Final Distance Below Reference Point (ft.) Drop in Water Level (in.) Percolation Rate (in/min) 0 1 1 8.01 8.20 2.28 2.28 1 2 1 8.20 8.37 2.04 2.04 2 3 1 8.37 8.49 1.44 1.44 0 1 1 8.02 8.20 2.16 2.16 1 2 1 8.20 8.34 1.68 1.68 2 3 1 8.48 8.48 1.68 1.68 Percolation Test Form Distance of the reference point above the bottom of the hole: Project Name:Graf St. Apartments Test Number:2 (TP-51 on map) Diameter of Test Hole:24"Depth of Test Hole:9.92 ft. Date and Time Soak Period Began: 4/3/20 @ 10:40 am Ended: 4/3/20 @ 11:45 am Date Test Began:4/3/2020 9.92 ft. Test Results Start Time of Day End Time of Day Time Interval (Minutes) Initial Distance Below Reference Point (ft.) Final Distance Below Reference Point (ft.) Drop in Water Level (in.) Percolation Rate (in/min) 0 1 1 7.10 7.42 3.84 2.28 1 2 1 7.42 7.60 2.16 2.04 2 3 1 7.60 7.74 1.68 1.44 0 1 1 2.60 4.21 19.32 2.16 1 2 1 4.21 5.40 14.28 1.68 2 3 1 5.40 6.05 7.80 1.68 Test #1 Test #2 Test #3 Avg. Infiltration Rate (in/min): Avg. Infiltration Rate w/ FS = 2: Infiltration Rate (in/min):2.28 2.16 3.84 2.76 1.38 *Did not use infiltration rate of 19.32 in/min as this was an outlier. Percolation Test Form Distance of the reference point above the bottom of the hole: Appendix D – Groundwater Monitoring Data and Geotech Report Figures REVISION F I G U R E D E S I G N E D B Y : Q U A L I T Y C H E C K : J O B N O . F I E L D B O O K D R A W N B Y : D A T E : B 1 9 - 0 1 4 B O R I N G M A P REV DATE N O T F O R C O N S T R U C T I O N GRAF STREET APARTMENTS BOZEMAN, MONTANA TEST PIT LOCATION MAP B 1 9 - 0 1 4 3 . 5 . 1 9 . D W G 1 D S O Engineering tdhengineering.com TEST PIT AND GROUND WATER DATA FIGURE DESIGNED BY: QUALITY CHECK: JOB NO. FIELDBOOK DRAWN BY: BJL DATE: B19-014 3.8.19 GR A F S T R E E T A P A R T M E N T S BO Z E M A N , M O N T A N A RE V D A T E RE V I S I O N NOT F O R CONS T R U C T I O N En g i n e e r i n g td h e n g i n e e r i n g . c o m B19-014 FIGURE 2 SU M M A R Y O F T E S T P I T S A N D G R O U N D W A T E R M O N I T O R I N G .DWG 2 Graf St. Apartments Groundwater Monitoring Summary *Measure from T.O.P.* Measured GW Measured GW Measured GW Measured GW 1 4966.35 2.00 4964.35 7.37 4958.98 7.57 4958.78 7.94 4958.41 7.73 4958.62 2 4970.85 1.50 4969.35 7.15 4963.70 7.25 4963.60 7.50 4963.35 3 4977.13 0.00 4977.13 4.65 4972.48 4.67 4972.46 4.85 4972.28 4 4981.20 2.50 4978.70 8.99 4972.21 9.08 4972.12 9.18 4972.02 9.14 4972.06 Measured GW Measured GW Measured GW Measured GW 1 4966.35 2.00 4964.35 6.54 4959.81 6.17 4960.18 6.64 4959.71 6.55 4959.80 2 4970.85 1.50 4969.35 7.48 4963.37 7.43 4963.42 7.39 4963.46 7.50 4963.35 3 4977.13 0.00 4977.13 4.80 4972.33 4.62 4972.51 4.64 4972.49 4.58 4972.55 4 4981.20 2.50 4978.70 8.95 4972.25 8.72 4972.48 8.91 4972.29 8.80 4972.40 Measured GW Measured GW Measured GW Measured GW 1 4966.35 2.00 4964.35 7.81 4958.54 6.76 4959.59 6.52 4959.83 2 4970.85 1.50 4969.35 7.61 4963.24 6.82 4964.03 7.06 4963.79 3 4977.13 0.00 4977.13 4.89 4972.24 4.64 4972.49 4.77 4972.36 4 4981.20 2.50 4978.70 9.12 4972.08 9.06 4972.14 9.02 4972.18 Well 1 Well 2 Well 3 Well 4 Well 1 Well 2 Well 3 Well 4 5/8/2020 4958.98 4972.21 5.37 6.49 5/15/2020 4958.78 4963.70 4972.48 4972.12 5.57 5.65 4.65 6.58 5/27/2020 4958.41 4963.60 4972.46 4972.02 5.94 5.75 4.67 6.68 6/5/2020 4958.62 4963.35 4972.28 4972.06 5.73 6.00 4.85 6.64 6/12/2020 4959.81 4963.37 4972.33 4972.25 4.54 5.98 4.80 6.45 6/19/2020 4960.18 4963.42 4972.51 4972.48 4.17 5.93 4.62 6.22 6/26/2020 4959.71 4963.46 4972.49 4972.29 4.64 5.89 4.64 6.41 7/3/2020 4959.80 4963.35 4972.55 4972.40 4.55 6.00 4.58 6.30 7/13/2020 4958.54 4963.24 4972.24 4972.08 5.81 6.11 4.89 6.62 7/20/2020 4959.59 4964.03 4972.49 4972.14 4.76 5.32 4.64 6.56 7/27/2020 4959.83 4963.79 4972.36 4972.18 4.52 5.56 4.77 6.52 Min 4.17 5.32 4.58 6.22 Max 5.94 6.11 4.89 6.68 Groundwater Elevation (ft) Groundwater Depth (ft) Groundwater Depths Summary Date 5/15/2020 5/27/2020 6/5/2020 Monitoring Well Top of Pipe Elevation Top of Casing to Ground (ft) Grnd Elevation @ Pipe Base 5/8/2020 6/19/2020 6/26/2020 7/3/2020 Monitoring Well Top of Pipe Elevation Top of Casing to Ground (ft) Grnd Elevation @ Pipe Base 7/13/2020 7/20/2020 7/27/2020 Monitoring Well Top of Pipe Elevation Top of Casing to Ground (ft) Grnd Elevation @ Pipe Base 6/12/2020 Appendix E – Detention and Retention Calculations 2131 Graf Pervious Paver Detention System Stormwater Detention Basin Calculation Basin 1 Calculation of Required Volume for Storm Water Infitration System Design Rainfall Freq.10 year IDF coefficient a 0.64 IDF coefficient b IDF coefficient n 0.65 Post-development Calculations Basin Area (ft2)160,623 total area:3.69 acres composite C:0.71 Infiltration Calculation Width of Paver =9 ft Length of Pavers =145.00 ft Infiltration Surface Area = 1,305 ft2 Infitration Rate =1.38 inch/min 1/2 of field measurement 0.00192 f/s Infiltration Rate Volumetric Infiltration Rate =2.50 cfs Storm Duration Intensity Future Runoff Runoff Release Required (minutes)(in/hr)Rate (cfs)Volume (cf)Volume (cf)Storage (cf) 1 9.16 23.99 1439 150 1289 3 4.49 11.74 2114 450 1664 5 3.22 8.43 2528 750 1777 7 2.59 6.77 2844 1051 1793 9 2.20 5.75 3105 1351 1755 11 1.93 5.05 3331 1651 1680 13 1.73 4.53 3532 1951 1581 15 1.58 4.13 3713 2251 1462 17 1.45 3.80 3879 2551 1328 19 1.35 3.54 4033 2851 1182 21 1.27 3.32 4177 3152 1026 23 1.19 3.12 4312 3452 861 25 1.13 2.96 4440 3752 688 27 1.08 2.82 4561 4052 509 29 1.03 2.69 4677 4352 325 31 0.98 2.57 4787 4652 135 required detention storage (ft3) =1,793 Storage Volume Calculation Width of Basin =9 ft Length of Basin =145 ft Depth of Basin =3.5 ft *Excludes 6" thick Pavers Gross Basin Volume = 4,568 ft3 Volume (40% voids) =1,827 ft3 Top of Paver Elevation 4,965.68 ft High Groundwater Elev.4,961.25 ft *Estimated by a groundwater surface generated from monitored Bottom of Detention Elev 4,961.68 ft seasonal high groundwater data 2131 Graf Pervious Paver Detention System Stormwater Detention Basin Calculation Basin 2 Calculation of Required Volume for Storm Water Infitration System Design Rainfall Freq.10 year IDF coefficient a 0.64 IDF coefficient b IDF coefficient n 0.65 Post-development Calculations Basin Area (ft2)15,581 total area:0.36 acres composite C:0.71 Infiltration Calculation Width of Paver =10 ft Length of Pavers =15.00 ft Infiltration Surface Area = 150 ft2 Infitration Rate =1.38 inch/min 1/2 of field measurement 0.00192 f/s Infiltration Rate Volumetric Infiltration Rate =0.29 cfs Storm Duration Intensity Future Runoff Runoff Release Required (minutes)(in/hr)Rate (cfs)Volume (cf)Volume (cf)Storage (cf) 1 9.16 2.33 140 17 122 3 4.49 1.14 205 52 153 5 3.22 0.82 245 86 159 7 2.59 0.66 276 121 155 9 2.20 0.56 301 155 146 11 1.93 0.49 323 190 133 13 1.73 0.44 343 224 118 15 1.58 0.40 360 259 101 17 1.45 0.37 376 293 83 19 1.35 0.34 391 328 64 21 1.27 0.32 405 362 43 23 1.19 0.30 418 397 22 25 1.13 0.29 431 431 -1 27 1.08 0.27 442 466 -23 29 1.03 0.26 454 500 -47 31 0.98 0.25 464 535 -70 required detention storage (ft3) =159 Storage Volume Calculation Width of Basin =10 ft Length of Basin =15 ft Depth of Basin =3.5 ft *Excludes 6" thick Pavers Gross Basin Volume = 525 ft3 Volume (40% voids) =210 ft3 Top of Paver Elevation 4,968.26 ft High Groundwater Elev.4,961.00 ft *Estimated by a groundwater surface generated from monitored Bottom of Detention Elev 4,964.26 ft seasonal high groundwater data 2131 Graf Pervious Paver Detention System Stormwater Detention Basin Calculation Basin 3 Calculation of Required Volume for Storm Water Infitration System Design Rainfall Freq.10 year IDF coefficient a 0.64 IDF coefficient b IDF coefficient n 0.65 Post-development Calculations Basin Area (ft2)51,818 total area:1.19 acres composite C:0.71 Infiltration Calculation Width of Paver =8 ft Length of Pavers =54.00 ft Infiltration Surface Area = 432 ft2 Infitration Rate =1.38 inch/min 1/2 of field measurement 0.00192 f/s Infiltration Rate Volumetric Infiltration Rate =0.83 cfs Storm Duration Intensity Future Runoff Runoff Release Required (minutes)(in/hr)Rate (cfs)Volume (cf)Volume (cf)Storage (cf) 1 9.16 7.74 464 50 415 3 4.49 3.79 682 149 533 5 3.22 2.72 815 248 567 7 2.59 2.18 917 348 570 9 2.20 1.86 1002 447 555 11 1.93 1.63 1075 546 528 13 1.73 1.46 1139 646 494 15 1.58 1.33 1198 745 453 17 1.45 1.23 1252 845 407 19 1.35 1.14 1301 944 357 21 1.27 1.07 1348 1043 304 23 1.19 1.01 1391 1143 249 25 1.13 0.95 1432 1242 190 27 1.08 0.91 1471 1341 130 29 1.03 0.87 1509 1441 68 required detention storage (ft3) =570 Storage Volume Calculation Width of Basin =8 ft Length of Basin =54 ft Depth of Basin =3.5 ft *Excludes 6" thick Pavers Gross Basin Volume = 1,512 ft3 Volume (40% voids) =605 ft3 Top of Paver Elevation 4,968.77 ft High Groundwater Elev.4,964.50 ft *Estimated by a groundwater surface generated from monitored Bottom of Detention Elev 4,964.77 ft seasonal high groundwater data 2131 Graf Pervious Paver Detention System Stormwater Detention Basin Calculation Basin 4 Calculation of Required Volume for Storm Water Infitration System Design Rainfall Freq.10 year IDF coefficient a 0.64 IDF coefficient b IDF coefficient n 0.65 Post-development Calculations Basin Area (ft2)48,789 total area:1.12 acres composite C:0.71 Infiltration Calculation Width of Paver =15 ft Length of Pavers =38 ft Infiltration Surface Area = 570 ft2 Infitration Rate =1.38 inch/min 1/2 of field measurement 0.00192 f/s Infiltration Rate Volumetric Infiltration Rate =1.09 cfs Storm Duration Intensity Future Runoff Runoff Release Required (minutes)(in/hr)Rate (cfs)Volume (cf)Volume (cf)Storage (cf) 1 9.16 7.29 437 66 372 3 4.49 3.57 642 197 445 5 3.22 2.56 768 328 440 7 2.59 2.06 864 459 405 9 2.20 1.75 943 590 353 11 1.93 1.53 1012 721 291 13 1.73 1.38 1073 852 221 15 1.58 1.25 1128 983 145 17 1.45 1.16 1178 1114 64 19 1.35 1.07 1225 1245 -20 21 1.27 1.01 1269 1377 -108 23 1.19 0.95 1310 1508 -198 25 1.13 0.90 1349 1639 -290 27 1.08 0.86 1385 1770 -384 29 1.03 0.82 1421 1901 -480 31 0.98 0.78 1454 2032 -578 required detention storage (ft3) =445 Storage Volume Calculation Width of Basin =15 ft Length of Basin =38 ft Depth of Basin =2.0 ft *Excludes 6" thick Pavers Gross Basin Volume = 1,140 ft3 Volume (40% voids) =456 ft3 Top of Paver Elevation 4,970.24 ft High Groundwater Elev.4,967.50 ft *Estimated by a groundwater surface generated from monitored Bottom of Detention Elev 4,967.74 ft seasonal high groundwater data 2131 Graf Pervious Paver Detention System Stormwater Detention Basin Calculation Basin 5 Calculation of Required Volume for Storm Water Infitration System Design Rainfall Freq.10 year IDF coefficient a 0.64 IDF coefficient b IDF coefficient n 0.65 Post-development Calculations Basin Area (ft2)183,041 total area:4.20 acres composite C:0.71 Infiltration Calculation Width of Paver =30 ft Length of Pavers =50.00 ft Infiltration Surface Area = 1,500 ft2 Infitration Rate =1.38 inch/min 1/2 of field measurement 0.00192 f/s Infiltration Rate Volumetric Infiltration Rate =2.88 cfs Storm Duration Intensity Future Runoff Runoff Release Required (minutes)(in/hr)Rate (cfs)Volume (cf)Volume (cf)Storage (cf) 1 9.16 27.33 1640 173 1468 3 4.49 13.38 2409 518 1892 5 3.22 9.60 2881 863 2018 7 2.59 7.72 3241 1208 2033 9 2.20 6.55 3539 1553 1986 11 1.93 5.75 3796 1898 1899 13 1.73 5.16 4025 2243 1782 15 1.58 4.70 4231 2588 1644 17 1.45 4.33 4421 2933 1488 19 1.35 4.03 4596 3278 1319 21 1.27 3.78 4760 3623 1138 23 1.19 3.56 4914 3968 947 25 1.13 3.37 5060 4313 747 27 1.08 3.21 5198 4658 540 29 1.03 3.06 5330 5003 327 required detention storage (ft3) =2,033 Storage Volume Calculation Width of Basin =30 ft Length of Basin =50 ft Depth of Basin =3.5 ft *Excludes 6" thick Pavers Gross Basin Volume = 5,250 ft3 Volume (40% voids) =2,100 ft3 Top of Paver Elevation 4,974.24 ft High Groundwater Elev.4,967.75 ft *Estimated by a groundwater surface generated from monitored Bottom of Detention Elev 4,970.24 ft seasonal high groundwater data 2131 Graf Pervious Paver Detention System Stormwater Detention Basin Calculation Basin 6 Calculation of Required Volume for Storm Water Infitration System Design Rainfall Freq.10 year IDF coefficient a 0.64 IDF coefficient b IDF coefficient n 0.65 Post-development Calculations Basin Area (ft2)126,106 total area:2.89 acres composite C:0.71 Infiltration Calculation Width of Paver =32 ft Length of Pavers =36.00 ft Infiltration Surface Area = 1,152 ft2 Infitration Rate =1.38 inch/min 1/2 of field measurement 0.00192 f/s Infiltration Rate Volumetric Infiltration Rate =2.21 cfs Storm Duration Intensity Future Runoff Runoff Release Required (minutes)(in/hr)Rate (cfs)Volume (cf)Volume (cf)Storage (cf) 1 9.16 18.83 1130 132 997 3 4.49 9.22 1660 397 1262 5 3.22 6.62 1985 662 1322 7 2.59 5.32 2233 927 1305 9 2.20 4.51 2438 1192 1246 11 1.93 3.96 2615 1457 1158 13 1.73 3.55 2773 1722 1051 15 1.58 3.24 2915 1987 928 17 1.45 2.99 3046 2252 794 19 1.35 2.78 3167 2517 650 21 1.27 2.60 3280 2782 497 23 1.19 2.45 3386 3047 339 25 1.13 2.32 3486 3312 174 27 1.08 2.21 3581 3577 4 29 1.03 2.11 3672 3842 -170 required detention storage (ft3) =1,322 Storage Volume Calculation Width of Basin =32 ft Length of Basin =36 ft Depth of Basin =3.0 ft *Excludes 6" thick Pavers Gross Basin Volume = 3,456 ft3 Volume (40% voids) =1,382 ft3 Top of Paver Elevation 4,972.84 ft High Groundwater Elev.4,969.00 ft *Estimated by a groundwater surface generated from monitored Bottom of Detention Elev 4,969.34 ft seasonal high groundwater data 2131 Graf Gravel Infiltration System Stormwater Detention Basin Calculation Basin 7 Calculation of Required Volume for Storm Water Infitration System Design Rainfall Freq.10 year IDF coefficient a 0.64 IDF coefficient b IDF coefficient n 0.65 Post-development Calculations Basin Area (ft2)82,565 total area:1.90 acres composite C:0.71 Infiltration Calculation Area of Grave infiltration swale 616 ft Infiltration Surface Area = 616 ft2 Infitration Rate =1.38 inch/min 1/2 of field measurement 0.00192 f/s Infiltration Rate Volumetric Infiltration Rate =1.18 cfs Storm Duration Intensity Future Runoff Runoff Release Required (minutes)(in/hr)Rate (cfs)Volume (cf)Volume (cf)Storage (cf) 1 9.16 12.33 740 71 669 3 4.49 6.04 1087 213 874 5 3.22 4.33 1299 354 945 7 2.59 3.48 1462 496 966 9 2.20 2.96 1596 638 959 11 1.93 2.59 1712 779 933 13 1.73 2.33 1815 921 894 15 1.58 2.12 1909 1063 846 17 1.45 1.96 1994 1204 790 19 1.35 1.82 2073 1346 727 21 1.27 1.70 2147 1488 660 23 1.19 1.61 2217 1629 587 25 1.13 1.52 2282 1771 511 27 1.08 1.45 2345 1913 432 29 1.03 1.38 2404 2054 350 required detention storage (ft3) =966 Storage Volume Calculation Area of Gravel Infiltration =616 ft Depth of Basin =4.0 ft Gross Basin Volume = 2,464 ft3 Volume (40% voids) =986 ft3 Top of Storage Elevation 4,965.00 ft High Groundwater Elev.4,961.00 ft *Estimated by a groundwater surface generated from monitored Bottom of Storage Elev 4,961.00 ft seasonal high groundwater data 2131 Graf Pervious Paver Detention System Stormwater Detention Basin Calculation Basin 8 Calculation of Required Volume for Storm Water Infitration System Design Rainfall Freq.10 year IDF coefficient a 0.64 IDF coefficient b IDF coefficient n 0.65 Post-development Calculations Basin Area (ft2)17,555 total area:0.40 acres composite C:0.71 Infiltration Calculation Area of Permeable Pavers 154 ft Infiltration Surface Area = 154 ft2 Infitration Rate =1.38 inch/min 1/2 of field measurement 0.00192 f/s Infiltration Rate Volumetric Infiltration Rate =0.30 cfs Storm Duration Intensity Future Runoff Runoff Release Required (minutes)(in/hr)Rate (cfs)Volume (cf)Volume (cf)Storage (cf) 1 9.16 2.62 157 18 140 3 4.49 1.28 231 53 178 5 3.22 0.92 276 89 188 7 2.59 0.74 311 124 187 9 2.20 0.63 339 159 180 11 1.93 0.55 364 195 169 13 1.73 0.49 386 230 156 15 1.58 0.45 406 266 140 17 1.45 0.42 424 301 123 19 1.35 0.39 441 336 104 21 1.27 0.36 457 372 85 23 1.19 0.34 471 407 64 25 1.13 0.32 485 443 43 27 1.08 0.31 499 478 20 29 1.03 0.29 511 514 -2 required detention storage (ft3) =188 Storage Volume Calculation Area of Pavers =154 ft Depth of Basin =3.5 ft *Excludes 6" thick Pavers Gross Basin Volume = 539 ft3 Volume (40% voids) =216 ft3 Top of Paver Elevation 4,976.50 ft High Groundwater Elev.4,968.00 ft *Estimated by a groundwater surface generated from monitored Bottom of Detention Elev 4,972.50 ft seasonal high groundwater data 2131 Graf 8/10/2020 Stormwater Retention Basin Calculation Basins 9 & 10 Calculation of Required Volume for Underground Storm Water Retention System Areas (ft2):Total: 130,752 total area: 3.00 acres composite C: 0.71 Required Retention Pond Calculations: Q = CIA C = 0.71 (post-development) I = 0.41 in/hr (Figure I-3, Pg 32, 10-yr, 2-hr storm) A = 3.00 acres Q =0.87 cfs required retention storage (ft3) =6,291 ft3 Contech Corrugated CMP Pipe Storage Calculations Pipe Area A = 3.14 x R2 Diameter Radius 3 1.5 3.14 = 7.07 ft2 Pipe Volume A = 3.14 x R2 Diameter Radius 3 1.5 3.14 = 7.07 ft2 Length (6-rows @ 70' each)=420 ft Volume = 2,967 ft3 Stone Volume Stone Width = 5.5 ft Stone Depth = 5 ft Area = 27.5 ft2 Less Pipe Area = 7.07 ft2 Stone Area = 20.44 ft2 Pipe Length =420 ft Storage Volume in Stone (40% voids)=3,433 ft3 Total Storage Volume =6,400 ft3 Bottom of Storage Elevation = 4,963.0 ft Seasonal High Groundwater Elevation = 4,962.5 ft 0.5" Rainfall Required Retention Calculations Area 130,752 sf Rainfall 0.5 inches 0.042 ft Volume to be Retained 5,448 cf 10-yr 2-hr Storm Controls Retention Calc.xls 2131 Graf Gravel Infiltration System Stormwater Detention Basin Calculation Basin 11 Calculation of Required Volume for Storm Water Infitration System Design Rainfall Freq.10 year IDF coefficient a 0.64 IDF coefficient b IDF coefficient n 0.65 Post-development Calculations Basin Area (ft2)22,915 total area:0.53 acres composite C:0.71 Infiltration Calculation Area of Gravel Swale 180 ft Infiltration Surface Area = 180 ft2 Infitration Rate =1.38 inch/min 1/2 of field measurement 0.00192 f/s Infiltration Rate Volumetric Infiltration Rate =0.35 cfs Storm Duration Intensity Future Runoff Runoff Release Required (minutes)(in/hr)Rate (cfs)Volume (cf)Volume (cf)Storage (cf) 1 9.16 3.42 205 21 185 3 4.49 1.68 302 62 239 5 3.22 1.20 361 104 257 7 2.59 0.97 406 145 261 9 2.20 0.82 443 186 257 11 1.93 0.72 475 228 248 13 1.73 0.65 504 269 235 15 1.58 0.59 530 311 219 17 1.45 0.54 553 352 202 19 1.35 0.50 575 393 182 21 1.27 0.47 596 435 161 23 1.19 0.45 615 476 139 25 1.13 0.42 633 518 116 27 1.08 0.40 651 559 92 29 1.03 0.38 667 600 67 required detention storage (ft3) =261 Storage Volume Calculation Area of Pavers =180 ft Depth of Basin =4.0 ft Gross Basin Volume = 720 ft3 Volume (40% voids) =288 ft3 Top of Storage Elevation 4,966.00 ft High Groundwater Elev.4,960.00 ft *Estimated by a groundwater surface generated from monitored Bottom of Storage Elev 4,962.00 ft seasonal high groundwater data Appendix F – Stormwater Maintenance Plan STORMWATER MAINTENANCE PLAN 2131 Graf The recommended stormwater facility maintenance is displayed below. It is the Property Owner’s Associations responsibility for routine inspection and maintenance of the following items: 1. Keep the sidewalk chases, curb & gutter, and swales free of leaves, litter, and other debris. 2. Keep the inlets of the facilities free of leaves, rocks, and other debris. 3. Quarterly inspect and clean curb inlets and pipes. 4. Remove sediment from the curb inlet sumps located on S 21st Ave by hand during the summer months whenever sediment has accumulated to greater than 9” in the bottom of the basin, refer to sheet C1.5 included in the stormwater report for location of curb inlets. 5. The Permeable Paver infiltration systems are to be inspected and maintained per the attached Powerblock Permeable Pavement System Guide Construction Specification, Part 4 - Inspection and Maintenance, or approved equivalent. The Permeable Paver infiltration systems are displayed on Sheets C1.5 & C1.6 and corresponding Basins are shown on sheet SD1.1, included in the stormwater report. 6. The Area Drain Inlets and Perforated Pipe with Drain Rock infiltration systems are to be maintained by the owner. The area drains should be inspected quarterly and kept free from debris, leaves, litter, and other debris. The perforated pipe should be inspected yearly and sediment should be removed from the pipes if necessary. The infiltration systems are displayed on sheets C1.5 & C1.6 and corresponding Basins are shown on sheet SD1.1, included in the stormwater report. 6. The buried retention systems are displayed on Sheet C1.5 of the stormwater report. The buried retention system maintenance is as follows: Minimum required maintenance includes a quarterly inspection during the first year of operation and a yearly inspection thereafter. Utilize inspection ports for inspections. The inspection ports can be used to pump water into the system and re- suspend accumulated sediment so that is may be pumped out. Flush and pump as inspections deem necessary. 7. Waste shall be disposed of from maintenance of facilities in accordance with applicable federal, state and local laws and regulations. 8. Property Owner’s Association to maintain and fund Operation and Maintenance of facilities. _______________________________ Property Owners Association PowerBlock® Permeable Pavement System Guide Construction Specification PART 1 GENERAL 1. Related Documents A. Drawings, technical specifications, and general provisions of the Contract as modified herein apply to this section. 2. Description of the Work Included A. Provide excavation and base preparation per geotechnical engineer's recommendations and/or as shown on the design drawings. B. Provide and install PowerBlock® and all related products including base materials, geotextiles, and geogrids per the manufacturer’s installation guidelines provided in this section. C. Perform post-installation testing. D. Protect PowerBlock® system from contamination due to construction traffic and construction sedimentation after installation until the site is completely stabilized. 3. Quality Assurance A. Installation Contractor shall demonstrate the following experience: 1. A minimum of three permeable pavement projects completed within the last 2 years of a similar or larger size and complexity. 2. A minimum of 25,000 square feet of permeable pavement installed within the last 2 years. 3. Installation Contractor experience requirement may be waived if the manufacturer’s representative provides on-site training and review during construction. B. Installation Personnel: Performed only by skilled workers with a satisfactory record of performance on permeable pavement construction projects of comparable size and complexity. C. Contractor must have the manufacturer’s representative available for site review if requested by the Owner. 4. Submittals A. Submit proposed PowerBlock® layout drawings. B. Submit manufacturer’s product data, including all requirements detailed in this specification. C. Submit material specifications for all geotextiles and geogrids. D. Submit material specification for base stone and aggregates. E. Any proposed equal alternative product substitution to this specification must be submitted for review and approved prior to the bid opening. The review package should include third party performance data that meets or exceeds the criteria in Table 2.1A. 5. Storage and Handling A. Protect concrete pavers during shipment, storage, and installation against staining, chipping, cracking, and other damage. B. Coordinate delivery and paving schedule with other construction activities. 6. Preinstallation Conference A. Prior to the start of the installation, a preinstallation conference shall occur with Owner representatives, the general contractor, the installation contractor, and the manufacturer’s representative. B. Coordinate installation for the PowerBlock® system with other on-site activities to minimize sedimentation and contamination of the permeable pavement during construction. All non-installation related construction traffic, particularly equipment used for earthwork, should be routed around the permeable pavement. Stabilize denuded soils contributing runoff to the permeable pavement prior to commissioning the system. PART 2: PRODUCTS 1. Permeable Paver A. Permeable pavement shall be constructed from pre-manufactured, interlocking concrete blocks that do not require stone or sand filler between the blocks, leaving the joints open to allow rapid infiltration of runoff through the joints. The blocks and completed permeable pavement shall meet the following properties: Table 2.1A PROPERTY DESCRIPTION VALUE Dimensions Length x Width x Height 11.75” x 13.70” x 4.5” (+/- 1/8”) Block Weight Pounds 44 lbs Minimum Loading Capability Traffic Rating HS-20 / HS-25 Open Joint Width Inches 0.25” (+/- 0.02”) Joint Filler Between Blocks Material Used NONE ALLOWED1 Post-Installation, Field- Verified Surface Infiltration Rate3 ASTM C-1701 / C-1701-M09 / ASTM C-1781 / C-140 1,000 inches / hour average (Minimum 3 tests) Compressive Strength ASTM D-6684 / C-140 4,000 psi (average) 3,500 psi (minimum) Freeze / Thaw Resistance2 ASTM C-67 / C-1645 / C-936 COMPLIANT Abrasion Resistance2 C-4182 COMPLIANT NOTE 1: No filler material is allowed to be used between the blocks. Use ONLY blocks that do not require stabilizing stone/sand between the units. NOTE 2: Testing by the National Concrete Masonry Association (NCMA) will be made available for freeze/thaw and abrasion resistance upon request. NOTE 3: The completed permeable pavement system must be tested in-situ after installation and will only be accepted when required performance value shown in Table 2.1A has been documented by a third party. Final test report must be submitted to the Owner prior to acceptance. B. Visual Inspection 1. All blocks shall be sound and free of defects that would interfere with the proper placing of the units or impair the strength or performance of the permeable pavement system. 2. Surface cracks incidental to the usual methods of manufacture, or surface chipping resulting from customary methods of handling in shipment and delivery, shall not be deemed grounds for rejection. 3. Cracks exceeding 0.25 inches in width and/or 1.0 inches in depth or larger shall be deemed grounds for rejection. 4. Ensure the PowerBlock delivered to the site matches the color requirements on plans. C. The permeable paver shall be PowerBlock® or pre-approved equal (as noted in Part 1, Section 4.E), as represented and distributed by: ACF Environmental PH. (800) 448-3636 info@acfenv.com acfenvironmental.com D. When PowerBlock® installation may be exposed to de-icing salts or salt air in coastal climates, blocks should be sealed after installation with optional Prossoco Saltguard WB or equivalent. If specified, the coating shall be applied per manufacturer’s recommendations. 2. Stone Base A. Permeable pavements require site specific design based on both structural and hydrologic requirements of the pavement. Depths shown on typical drawings must be evaluated and modified as necessary by the engineer of record. B. All aggregate shall be clean and angular on all sides, with no less than 90% fractured faces. Do not use rounded river gravel or fractured river gravel for any application. C. If more than 6” of base stone is required, use AASHTO #2 Stone or simillar for the lower layers. ASTM No. 2 Subbase Grading Requirements Sieve Size Percent Passing 75 mm (3 in.) 100 63 mm (2 1/2 in.) 90 to 100 50 mm (2 in.) 35 to 70 37.5 mm (1 1/2 in.) 0 to 15 19 mm (3/4 in.) 0 to 5 D. AASHTO #57 Stone shall be used as a leveling course for the upper 4” to 6” of the base layer. ASTM No. 57 Base Grading Requirements Sieve Size Percent Passing 37.5 mm (1 1/2 in.) 100 25 mm (1 in.) 95 to 100 12.5 mm (1/2 in.) 25 to 60 4.75 mm (No. 4) 0 to 10 2.36 mm (No. 8) 0 to 5 3. Geotextiles A. Use a woven monofilament geotextile, such as ACF M200, or as specified in the contract documents. 4. Edge Restraint A. Perimeter: Edges of the PowerBlock area shall be finished with a Standing Curb with a vertical face, or as shown on plans B. Internal Edges: Edges of the PowerBlock area where traffic access is required shall be finished with a flush Ribbon Curb, or as shown on plans. PART 3: FOUNDATION PREPARATION AND BLOCK INSTALLATION 1. Foundation & Preparation A. Prepare subgrade as noted on plans. Typically, compaction of underlying subgrade soil should be avoided or minimized in order to encourage infiltration of stormwater. Subgrade should be uniform, level, and free of lumps and debris. All questions about the adequacy of the subgrade should be directed to the owner’s engineer, who will approve the subgrade conditions prior to placement of the stone base. B. Place a woven monofilament geotextile, such as ACF M200, on the subgrade base and sides of the excavation to prevent contamination of the clean aggregate base or as specified in the contract documents. Overlap seams a minimum of 12” in all directions, or as shown on plans. C. Install base materials in layers uniformly spread and compacted in 6” – 8” lifts or as noted on plans. When final layer of base stone is installed, compact first with a roller and finish with a 10,000 psi plate compactor in both the perpendicular and parallel directions. Compaction is complete when no movement of base materials is observed. Base shall be a smooth, plane surface, firm and non-yielding prior to placement of the PowerBlock®. D. Confirm finished elevations of the base match plan requirements. E. Completed base shall be proof rolled and inspected and approved by engineer or record. Reconstruct areas where deflection exceeds acceptable limits as determined by engineer. 2. Pavers A. Ensure PowerBlock® units are free of foreign material before installation. B. Set PowerBlock® pavers as shown on plans, within the specified lines and grades shown on plans. Units shall be installed straight and true to the required lines. Ensure joint widths are consistent throughout installation. 1. Installation shall proceed by adding blocks adjacent to previously installed units. 2. On sloped areas, work from lower areas toward the higher elevations. C. Cut PowerBlock® units as needed to accommodate field conditions and to achieve a consistent pattern. D. When a substantial area of PowerBlock® units has been installed, the pavers shall be static rolled to ensure a consistent top elevation. E. Replace pavers that are broken, substantially chipped, or stained during construction. F. The joints between the blocks shall not be backfilled with smaller aggregates or sand in order to function properly. The joints shall be left open at all times, including following maintenance of the permeable pavement. G. Within 60 days of completion of the installation, the surface infiltration rate of the pavement shall be field verified to confirm the required infiltration rate of the pavement (per Table 2.1A). If the system fails to perform as required, it shall be removed and replaced at no cost to the Owner. PART 4: INSPECTION AND MAINTENANCE 1. Inspection A. Inspect the permeable pavement, noting areas of standing water or significant accumulation of joint debris. B. If joints are excessively filled with debris or sediment, a surface infiltration test may be performed per Table 2.1A to determine the capabilities of the system. 2. Maintenance A. Maintenance shall be performed when either: 1. The surface infiltration rates of more than 75% of the surface area fall below 10% of the rate required per Table 2.1A. 2. Surface ponding remains for 24 hours in an area larger than 10 square feet. 3. Other desired maintenance at the Owner’s discretion to optomize performance. B. Maintenance shall be performed with a vacuum device, not a mechanical sweeper, to remove accumulated debris from joints. This may be accomplished with smaller hand-held devices or with vacuum trucks such as the Elgin Whirlwind. Adjust device settings to avoid movement or lifting of block, or removal of the base stone underneath the blocks at all times.